Temperature effects on byssal thread production in the mussel, Mytilus trossulus

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Abstract

Mussels attach themselves to hard substrates by extruding thin, strong, and flexible hair- like attachments known as byssal threads, which are anchored in place with small adhesive plaques. While many studies have examined how multiple abiotic variables affect mussel attachment strength, few have performed extensive single variable tests within a controlled lab setting. In this study, we investigated the effects of temperature on byssus production in the native Northern Pacific intertidal blue mussel, Mytilus trossulus, and expected to see a decline in production with increasing temperatures (specifically, between 18°C-25°C). We also hypothesized that threads produced in warmer temperatures would show a visual decline in quality, either through thinning, degradation, or tearing. Mussels were placed in a temperature controlled flume for 24 hours. Six different trials were run at 10°C, 14°C, 18°C, 20°C, 22°C, and 25°C. Byssal threads were counted for the duration of each trial to determine production and rate of attachment. Threads produced under these different temperature regimes were analyzed under an SEM to visually compare differences in quality. Overall, there was a significantly negative correlation between thread production and increases in temperature, with the highest amount occurring at 18°C (11.25 threads +2.0 s.e.m.) and the lowest at 25°C (0 threads). Acclimatization and rate of thread production was also negatively affected by temperature increases. In addition, we saw a significant difference in percentage of mussel attachment between temperatures, with up to 93% attached in the 10°C and 18°C treatments and 50-0% in the 20°C-25°C treatments. However, visual analyses of thread quality differences were inconclusive. Our findings indicate that climatic temperature increases may negatively affect both the range of M. trossulus within Northern Pacific rocky intertidal zones as well as economically setback the aquaculture of the speciess.